The overall objective of this project is to investigate the cause(s) of infertility observed in association with obesity. For this purpose the genetically obese "Fatty" rat is being used as a model to study some of the characteristics of the hypothalamus pituitary, ovary and uterus to isolate the defect(s) that may be the cause(s) for infertility. Goals for the current year are: 1) to study the natural mating response; 2) to study the uterine response to estrogen and progesterone; 3) to study the characteristics of estrogen and progesterone receptors of the uterus, pituitary and hypothalamus; 4) to study deciduomata formation in the uterus in response to exogenous hormones; 5) to induce obesity in Sprague-Dawley rats in response to gold thioglucose in order to use these rats as controls for genetic obese rats.